Illumination device

ABSTRACT

An illumination device ( 10 ) includes: a light diffusion device ( 50 ) including element diffusion devices ( 55 ) that diffuse incident light; a coherent light source ( 15 ) that emits coherent light; a shaping optical system ( 20 ) that shapes the coherent light; a scanner ( 30 ) that adjusts a traveling direction of the coherent light so as to allow the coherent light to scan the light diffusion device; and a light condensing optical system located on a light path of the coherent light from the shaping optical system up to the light diffusion device. The light condensing optical system condenses the coherent light such that a spot area on the light diffusion device is smaller than the element diffusion device. Each element diffusion device diffuses the coherent light incident thereon so as to illuminate an element illumination area corresponding to the element diffusion device.

TECHNICAL FIELD

The present invention relates to an illumination device that illuminatesa predetermined area by using light.

BACKGROUND ART

As disclosed in JP2012-146621A, for example, an illumination deviceusing a coherent light source is widely used. A laser light source thatoscillates laser light (laser beam) is typically used as the coherentlight source.

JP2012-146621A discloses a vehicle lighting tool. The vehicle lightingtool includes a light source, which can be formed by a laser oscillationdevice, and four hologram devices. The respective hologram devices aremoved by a rotating and driving apparatus to be located on positionswhere they can receive laser light from the light source. The respectivehologram devices diffract the laser light to achieve illumination in adesired light distribution pattern. By suitably selecting a hologramdevice which is irradiated with laser light, illumination in apredetermined light distribution pattern can be achieved. In the vehiclelighting tool, in order to prevent that an unintended area is irradiatedwith illumination light, it is necessary to control irradiation of laserlight while the locations of the four hologram devices are changed. Inthis case, a period of time in which the light source stops emission oflight becomes long. Thus, it is impossible to sufficiently utilizeperformance of the light source so as to illuminate an illumination areawith a sufficiently bright quantity of light.

DISCLOSURE OF INVENTION

The present invention has been made in consideration of the above point.The first object of the present invention is to provide an illuminationdevice that can sufficiently utilize performance of a coherent lightsource so as to brightly illuminate an illumination area in a desiredlight distribution pattern.

In addition, the present invention has been made in consideration of theabove point, and the second object thereof is to provide an illuminationdevice that can sufficiently utilize performance of a light source,which is not limited to a coherent light source, so as to brightlyilluminate an illumination area in a desired light distribution pattern.

An illumination device according to a first embodiment of the presentinvention is an illumination device comprising:

a light diffusion device including element diffusion devices thatdiffuse incident light;

a coherent light source that emits coherent light;

a shaping optical system that shapes the coherent light;

a scanner that adjusts a traveling direction of the coherent light so asto allow the coherent light to scan the light diffusion device; and

a light condensing optical system located on a light path of thecoherent light from the shaping optical system up to the light diffusiondevice;

wherein:

the light condensing optical system condenses the coherent light suchthat a spot area on the light diffusion device is smaller than theelement diffusion device; and

each element diffusion device diffuses the coherent light incidentthereon so as to illuminate an element illumination area correspondingto the element diffusion device.

In the illumination device according to the first embodiment of thepresent invention,

the shaping optical system may divide the coherent light emitted fromthe coherent light source into light fluxes; and

the light condensing optical system may adjust light paths of the lightfluxes such that the light fluxes are overlapped at least partially onthe light diffusion device.

In the illumination device according to the first embodiment of thepresent invention, the light condensing optical system may include alens, and the light diffusion device may be located on a focus positionof the lens.

In the illumination device according to the first embodiment of thepresent invention, the shaping optical system may include a collimationlens, and a lens array located on a light path from the collimation lensup to the light condensing optical system.

In the illumination device according to the first embodiment of thepresent invention,

the lens array may include element lenses; and

light fluxes emergent from the element lenses may have the same lightdistributions.

In the illumination device according to the first embodiment of thepresent invention, the shaping optical system may have a beamhomogenizer.

The illumination device according to the first embodiment of the presentinvention may further comprise an emission control unit that controlsemission of the coherent light from the coherent light source.

In the illumination device according to the first embodiment of thepresent invention, the emission control unit may control emission of thecoherent light of the coherent light source, depending on an irradiationposition of the coherent light on the light diffusion device.

In the illumination device according to the first embodiment of thepresent invention,

the light diffusion device may have a hologram storage medium; and

the element diffusion devices may be element holograms havinginterference fringe patterns different from one another.

In the illumination device according to the first embodiment of thepresent invention,

the light diffusion device may have a lens array group including aplurality of lens arrays; and

the element diffusion devices may have the lens arrays.

According to the first embodiment of the present invention, theillumination device can sufficiently utilize performance of the coherentlight source so as to brightly illuminate an illumination area in adesired light distribution pattern.

An illumination device according to a second embodiment of the presentinvention is an illumination device comprising:

a light deflection device including element deflection devices thatadjust a traveling direction of incident light;

a light source;

a diffusion optical system that diffuses light-source light emitted bythe light source;

a scanner that adjusts a traveling direction of the light-source lightso as to allow the light-source light to scan the light deflectiondevice; and

a light condensing optical system located on a light path of thelight-source light from the diffusion optical system up to the lightdeflection device;

wherein:

the light condensing optical system condenses the light-source lightsuch that a spot area on the light deflection device is smaller than theelement deflection device; and

each element deflection device adjusts a traveling direction of thelight-source light incident thereon so as to illuminate an elementillumination area corresponding to the element deflection device.

In the illumination device according to the second embodiment of thepresent invention,

the light diffusion optical system may divide the light-source lightinto light fluxes; and

the light condensing optical system may adjust light paths of the lightfluxes such that the light fluxes are overlapped at least partially onthe light deflection device.

In the illumination device according to the second embodiment of thepresent invention, the light condensing optical system may include alens, and the light deflection device may be located on a focus positionof the lens.

In the illumination device according to the second embodiment of thepresent invention, the diffusion optical system may include acollimation lens, and a lens array located on a light path from thecollimation lens up to the light condensing optical system.

In the illumination device according to the second embodiment of thepresent invention,

the lens array may include element lenses; and

light fluxes emergent from the element lenses may have the same lightdistributions.

In the illumination device according to the second embodiment of thepresent invention, the diffusion optical system may have a beamhomogenizer.

The illumination device according to the second embodiment of thepresent invention may further comprise an emission control unit thatcontrols emission of the light from the light-source.

In the illumination device according to the second embodiment of thepresent invention, the emission control unit may control emission oflight from the light-source, depending on an irradiation position of thelight-source light on the light deflection device.

In the illumination device according to the second embodiment of thepresent invention,

the light deflection device may have a diffraction grating array; and

each element deflection device may be diffraction grating.

In the illumination device according to the second embodiment of thepresent invention,

the light deflection device may have a prism array; and

each element deflection device may be prism.

According to the second embodiment of the present invention, theillumination device can sufficiently utilize performance of thelight-source so as to brightly illuminate an illumination area in adesired light distribution pattern.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view schematically showing an overall structureof an illumination device, for explaining a first embodiment of thepresent invention.

FIG. 2 is a plan view showing the illumination device of FIG. 1.

FIG. 3 is a plan view showing a scanner, a light condensing opticalsystem and a light diffusion device of the illumination device of FIG.1, mainly for explaining a function of the light condensing opticalsystem.

FIG. 4 is a view showing the light diffusion device and an illuminationarea that is illuminated with diffusion light from the light diffusiondevice in the illumination device of FIG. 1, for explaining a functionof the light diffusion device.

FIG. 5 is a plan view showing a spot area on the light diffusion device.

FIG. 6 is a plan view showing the spot area on the light diffusiondevice, with a shaping optical system and the light condensing opticalsystem being omitted.

FIG. 7 is a perspective view schematically showing an overall structureof an illumination device, for explaining a second embodiment of thepresent invention.

FIG. 8 is a plan view showing the illumination device of FIG. 7.

FIG. 9 is a plan view showing a scanner, a light condensing opticalsystem and a light deflection device of the illumination device of FIG.7, mainly for explaining a function of the light condensing opticalsystem.

FIG. 10 is a plan view showing the light deflection device of theillumination device of FIG. 7.

FIG. 11 is a view showing the light deflection device and anillumination area that is illuminated with light from the lightdeflection device in the illumination device of FIG. 7.

FIG. 12 is a plan view showing a spot area on the light deflectiondevice.

FIG. 13 is a plan view showing the spot area on the light deflectiondevice, with a diffusion optical system and the light condensing opticalsystem being omitted.

MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described herebelow withreference to the drawings. In the drawings attached to thespecification, a scale size, an aspect ratio and so on are changed andexaggerated from the actual ones, for the convenience of easiness inillustration and understanding

Further, terms specifying shapes, geometric conditions and theirdegrees, e.g., “parallel”, “perpendicular/orthogonal”, “same”, etc., arenot limited to their strict definitions, but are to be construed toinclude a range capable of exerting a similar function.

A first embodiment is firstly described with reference to an exampleshown in FIGS. 1 to 6.

FIG. 1 is a perspective view schematically showing an overall structureof an illumination device 10. The illumination device 10 illuminates anillumination area Z by using coherent light. The illumination device 10includes a laser light source 15 functioning as a coherent light source.The laser light source 15 oscillates laser light (laser beam) which isan example of coherent light. The illumination device 10 includes ashaping optical system 20, a scanner 30, a light condensing opticalsystem 40 and a light diffusion device 50, which process light emittedfrom the laser light source 15. In the example shown in FIG. 1, theshaping optical system 20, the scanner 30, the light condensing opticalsystem 40 and the light diffusion device 50 are located in this orderalong a light path of laser light from the laser light source 15, andthey process laser light in this order. As described in detail below,the illumination device 10 described herein can illuminate, with a largequantity of light, the illumination area Z in a desired lightdistribution pattern, while sufficiently utilizing the performance ofthe coherent light source by means of optical actions in the shapingoptical system 20 and the light condensing optical system 40. Herebelow,the respective constituent elements are sequentially described.

In the example shown in FIG. 1, the laser light source 15 has aplurality of light source units 17 that emit laser light. The lightsource units 17 may be independently arranged, or may be a light sourcemodule formed by arranging the light source units 17 side by side on acommon substrate. For example, the light source units 17 have a firstlight source unit 17 a that oscillates light of a red emissionwavelength range, a second light source unit 17 b that oscillates lightof a green emission wavelength range, and a third light source unit 17 cthat oscillates light of a blue emission wavelength range. According tothis example, since three laser lights (laser beams) emitted from thelight source units 17 a, 17 b and 17 c are overlapped, illuminationbeams of various colors including a white illumination beam can begenerated.

Although an example in which the laser light source 15 has the threelight source units 17 a, 17 b and 17 c having emission wavelength rangesdifferent from one another is described herebelow, the present inventionis not limited thereto. The laser light source 15 may have two lightunits 17 having emission wavelength ranges different from each other, orfour or more light units 17 having emission wavelength ranges differentfrom one another. In addition, in order to increase emission intensity,a plurality of the light source units 17 may be provided for eachemission wavelength range.

As shown in FIG. 1, the illumination device 10 includes an emissioncontrol unit 12 connected to the laser light source 15. The emissioncontrol unit 12 controls emission timings of laser lights (laser beams)emitted by the laser light source 15. In particular, the emissioncontrol unit 12 can switch emission of laser lights and stop of emissionof laser lights from the light source unit 17 a, 17 b or 17 c,independently from other light source units. The control of emitting ornot emitting laser lights by the emission control unit 12 is carried outbased on scanning timings of a plurality of laser lights by the scanner30, in other words, based on incident positions of laser lights on thelight diffusion device 50. As described above, in the case where thelaser light source 15 can emit three laser lights, i.e., a red laserlight, a blue laser light and a green laser light, it is possible togenerate illumination light of a color that is a combination of giventwo or more colors of red, blue and green, by controlling an emissiontiming of each laser light.

The emission control unit 12 may control whether a laser light isemitted from each light source unit 17 or not, i.e., ON/OFF of emission,or may switch blocking or not blocking of a light path of a laser lighthaving been emitted from each light source unit 17. In the latter case,light shutter units, not shown, may be disposed between the respectivelight source units 17 and the shaping optical system 20, such thatpassage and blockage of laser light can be switched by the light shutterunits.

Next, the shaping optical system 20 is described. The shaping opticalsystem 20 shapes laser light emitted from the laser light source 15. Inother words, the shaping optical system 20 shapes a cross-sectionalshape of laser light orthogonal to an optical axis, and athree-dimensional shape of a light flux of laser light.

FIG. 2 is a plan view showing the illumination device 10. As shown inFIG. 2, the shaping optical system 20 includes a beam expander 21, acollimation lens 22 and a lens array 23, in this order along a lightpath of laser light. The beam expander 21 shapes a laser light emittedfrom the laser light source 15 into a divergent light flux. Thecollimation lens 22 reshapes the divergent light flux generated by thebeam expander 21 into parallel light fluxes lf1. The lens array 23includes a plurality of element lenses 24 that are arranged on positionsfacing the collimation lens 22. The element lenses 24 are positionedsuch that an optical axis d₂₄ of each element lens 24 is parallel to anoptical axis d₂₂ of the collimation lens 22. In addition, the elementlenses 24 are arranged on a virtual face vl that is orthogonal to theoptical axis d₂₂ of the collimation lens 22. Each element lens 24 shapesa parallel light flux lf1, which has been shaped by the collimation lens22 and has entered the element lens 24, into a convergent light fluxlf2.

In the example shown in FIG. 2, the shaping optical system 20 divides alaser light emitted from the laser light source 15 into a plurality oflight fluxes lf2. The shaping optical system 20 divides a laser lightinto light fluxes lf2 the number of which is equal to the number of theelement lenses 24 included in the lens array 23. In the illustratedexample, each element lens 24 shapes a parallel light flux lf1, whichhas been shaped by the collimation lens 22 and has entered the elementlens 24, into a convergent light flux lf2. That is to say, respectivelight fluxes lf2 divided by the shaping optical system 20 are convergentlight fluxes. In addition, in the illustrated example, the elementlenses 24 have the same structures each other. Thus, light fluxes lf2emitted from the element lenses 24 are the same light distributions. Forexample, the light fluxes lf2 have the same convergent angles and thesame convergent positions, and optical axes d_(lf2) of the light fluxeslf2 are parallel to one another.

A plurality of the shaping optical systems 20 may be providedcorrespondingly to the respective light source units 17 included in thelaser light source 15. Alternatively, the single shaping optical system20 capable of adjusting light paths of laser lights from the lightsource units 17 a, 17 b and 17 c may be provided. In the example shownin FIG. 2, the light source units 17 a, 17 b and 17 c may be aligned inthe depth direction of the sheet plane of FIG. 2, the beam expander 21may diverge a laser light only in a plane of the sheet plane of FIG. 2,and the collimation lens 22 and the element lenses 24 of the lens array23 in the shaping optical system 20 may respectively be formed ascylindrical lenses extending to have a certain cross-sectional shape inthe depth direction of the sheet plane of FIG. 2. According to thisexample, the light source units 17 can share the collimation lens 22 andthe lens array 23.

Next, the scanner 30 is described. The scanner 30 adjusts a travelingdirection of a laser light emitted from the laser light source 15. Thescanner 30 changes a traveling direction of a laser light over time. Dueto the light path adjustment of the scanner 30, a laser light emittedfrom the laser light source 15 scans the light diffusion device 50. Inthe example shown in FIGS. 1 and 2, the scanner 30 is formed as apolygonal mirror 31 having six reflection surfaces. When the polygonalmirror 31 is rotated about its central axis line as a rotational axisline ra, a reflection direction of light that has entered there from acertain direction can be changed cyclically. The respective sixreflection surfaces of the polygonal mirror 31 are formed as flatsurfaces. Thus, as shown in FIG. 3, after three light fluxes lf3, whichhad been shaped by the shaping optical system 20, have been reflected bythe polygonal mirror 31 so that their traveling directions have beenchanged, optical axes d_(lf3) of the light fluxes lf3 remain parallel.FIG. 3 is a partially enlarged plan view showing a light path from thescanner 30 up to the light diffusion device 50.

In particular, in the illustrated example, the light source units 17 a,17 b and 17 c are aligned in a direction parallel to the rotational axisline ra of the polygonal mirror 31 (see FIG. 1). The reflection surfaceof the polygonal mirror 31 includes, along this rotational axis line ra,a first reflection unit 31 a, a second reflection unit 31 b and a thirdreflection unit 31 c. The first reflection unit 31 a reflects a laserlight emitted from the first light source unit 17 a and cyclicallychanges a traveling direction of the laser light in a plane orthogonalto the rotational axis line ra. In addition, the second reflection unit31 b reflects a laser light emitted from the second light source unit 17b, and the third reflection unit 31 c reflects a laser light emittedfrom the third light source unit 17 c.

As shown in FIG. 2, the polygonal mirror 31 is positioned with respectto the shaping optical system 20, such that the polygonal mirror 31reflects light from the shaping optical system 20 on a focus position ofeach element lens 24 of the lens array 23, or on a position closethereto. Thus, as shown in FIG. 3, light reflected from the polygonalmirror 31 substantially becomes a divergent light flux lf3 whosedivergent point is the reflection surface of the polygonal mirror 31.

The scanner 30 is not limited to the illustrated polygonal mirror 31. Itis possible to use, as the scanner 30, an apparatus thatthree-dimensionally changes in a biaxial direction a traveling directionof light incident thereon from a certain direction. For example, MEMS(micro electromechanical systems) such as a digital micromirror device(DMD) may be used as the scanner 30.

Next, the light condensing optical system 40 is described. The lightcondensing optical system 40 is located on a light path of a laser lightfrom the shaping optical system 20 up to the light diffusion device 50.The light condensing optical system 40 optically processes a laser lighthaving been shaped by the shaping optical system 20. The lightcondensing optical system 40 condenses the laser light, such that a spotarea S on the light diffusion device 50, i.e., an area, which isirradiated with a laser light on the light diffusion device 50 at acertain instance, has a smaller planar dimension.

In the illustrated example, the light condensing optical system 40 isformed by a light condensing lens 41 having a focus Pf. The lightcondensing lens 41 is located on a light path of a laser light from thesaner 30 toward the light diffusion device 50. As described above, theshaping optical system 20 divides a laser light into a plurality oflight fluxes lf3. As shown in FIG. 3, the optical axes d_(lf3) of thelight fluxes lf3 are parallel to one another. Thus, as shown in FIG. 3,because of a lens action of the light condensing lens 41, optical axesd_(lf4) of three light fluxes lf4 intersect on a position Px on avirtual face vlf that is apart from the light condensing lens 41 by afocus distance f₄₀ of the light condensing lens 41 along an optical axisd₄₀ of the light condensing lens 41. In the illustrated example, thelight diffusion device 50 is located on the virtual face vlf that isapart from the light condensing lens 41 by the focus distance f₄₀ of thelight condensing lens 41 along the optical axis d₄₀ of the lightcondensing lens 41. Thus, the three light fluxes lf3 having been shapedby the shaping optical system 20 are overlapped at least partially onthe light diffusion device 50, by the light condensing action of thelight condensing optical system 40.

In particular, in the illustrated example, as shown in FIG. 3, thescanner 30 and the light condensing optical system 40 are located suchthat the polygonal mirror 31 reflects a laser light from the shapingoptical system 20 on a position apart from the light condensing lens 41by the focus distance f₄₀ of the light condensing lens 41 along theoptical axis d₄₀ of the light condensing lens 41 or on a position closeto the position. Further, as described above, each of light fluxes lf3,which has been reflected by the polygonal mirror 31 and has entered thelight condensing optical system 40, is a divergent light flux lf3 whosedivergent point is located on the reflection surface of the polygonalmirror 31 or close thereto. Thus, each light flux lf3 passes through thelight condensing lens 41 so as to be converted to parallel fluxes lf4.As a result, the light fluxes lf4 having been shaped by the shapingoptical system 20 irradiate the same area on the light diffusion device50 by the light condensing function of the light condensing opticalsystem 40, i.e., the light fluxes lf4 are overlapped on the lightdiffusion device 50 highly precisely. Since the scanner 30 changestraveling directions of laser lights with time, a spot area S on whichthe light fluxes lf4 are condensed by the light condensing opticalsystem 40 changes its position over time on the light diffusion device50.

A plurality of the light condensing optical systems 40 may be providedcorrespondingly to the respective light source units 17 a, 17 b and 17 cincluded in the laser light source 15. Alternatively, the single lightcondensing optical system 40 capable of adjusting light paths of laserlights from the light source units 17 a, 17 b and 17 c may be provided.For example, when a laser light is diverged or converged only in a planeparallel to the sheet plane of FIG. 3, the light condensing lens 41forming the light condensing optical system 40 may be a cylindrical lensextending to have a certain cross-sectional shape in the depth directionof the sheet plane of FIG. 2. According to this example, the lightcondensing lens 41 can be shared by laser lights emitted by the lightsource units 17 a, 17 b and 17 c.

Next, the light diffusion device 50 is described. The light diffusiondevice 50 diffuses a laser light so as to illuminate a predeterminedrange. To be more specific, the laser light diffused by the lightdiffusion device 50 passes through an illumination area Z, and thenilluminates a predetermined range that is an actual illumination range.

The illumination area Z and an element illumination area Zp, which formsa part of the illumination area Z, are illumination areas of near fieldsthat are overlappingly illuminated by respective element diffusiondevices 55 in the light diffusion device 50. An illumination range of afar field is generally expressed as a diffusion angle distribution in anangular space, rather than an actual illumination area size. The terms“illumination area” and “element illumination area” in thisspecification include a diffusion angle range in an angular space inaddition to an actual illumination area (illumination range). Thus, apredetermined range illuminated by the illumination device 10 of FIGS. 1and 4 can be an area that is greatly larger than the illumination area Zof a near field shown in FIGS. 1 and 4.

FIG. 4 is a plan view showing the light diffusion device 50, togetherwith the illumination area Z to which light is directed by the lightdiffusion device 50. In the illustrated example, the light diffusiondevice 50 includes a first light diffusion device 50 a, a second lightdiffusion device 50 and a third light diffusion device 50 c,correspondingly to the fact that the laser light source 15 includes thefirst to third light source units 17 a, 17 b and 17 c. A laser lightfrom the first light source unit 17 a enters the first light diffusiondevice 50 a, a laser light from the second light source unit 17 b entersthe second light diffusion device 50 b, and a laser light from the thirdlight source unit 17 c enters the third light diffusion device 50 c. Byusing the laser lights that have entered the whole areas of therespective light diffusion devices 50 a, 50 b and 50 c so as to bediffused, the whole area of the common illumination area Z can beilluminated. Thus, the first light diffusion device 50 a directs redlight from the first light source unit 17 a toward the illumination areaZ, the second light diffusion device 50 b directs green light from thesecond light source unit 17 b toward the illumination area Z, and thethird light diffusion device 50 c directs blue light from the thirdlight source unit 17 c toward the illumination area Z, whereby theillumination area Z can be illuminated in white. As shown in FIG. 1, thelight diffusion devices 50 a, 50 b and 50 c are respectively formed tohave an elongate shape in a direction orthogonal to the rotational axisline ra of the polygonal mirror 31 forming the scanner 30. The lightdiffusion devices 50 a, 50 b and 50 c are arranged side by side in adirection orthogonal to their longitudinal directions.

As shown by the dotted lines in FIG. 4, each of the light diffusiondevices 50 a, 50 b and 50 c has a plurality of element diffusion devices55. Each element diffusion device 55 has a light path control functionfor directing light, which has been incident on each area in itsincident surface, toward a predetermined direction depending on aposition of the area. The element diffusion device 55 described hereincorrects a traveling direction of light incident on a given area or agiven position, and directs the light to a predetermined area. Namely,laser lights emitted to respective areas, which are obtained by planarlydividing the incident surface of the element diffusion device 55, passthrough the element diffusion device 55, and then illuminate areas thatare at least partially overlapped with each other.

In the illustrated example, light, which has entered a small area in theelement diffusion device 55 via the scanner 30, is diffused by theelement diffusion device 55 to illuminate the whole area of apredetermined element illumination area Zp. The element illuminationarea Zp forms a part of the illumination area Z. An element illuminationarea Zp corresponding to one element diffusion device 55 is not at leastpartially overlapped with an element illumination area Zp correspondingto another element diffusion device 55. Namely, an aggregation of theelement illumination areas Zp corresponding to a plurality of elementdiffusion devices 55 provides the illumination area Z that can beilluminated by the illumination device 10.

In the example shown in FIG. 4, nine element diffusion devices 55 arealigned along the longitudinal directions of the respective lightdiffusion devices 50 a, 50 b and 50 c. The illumination area Z isplanarly divided like a grid into nine element illumination areas Zp.That is to say, in the illustrated example, one element illuminationarea Zp is not overlapped with another element illumination area Zp.First element diffusion devices 55 a of the respective light diffusiondevices 50 a, 50 b and 50 c illuminate a first element illumination areaZp1. Similarly, second to ninth element diffusion devices 55 b to 55 iof the respective light diffusion devices 50 a, 50 b and 50 c illuminatesecond to ninth element illumination areas Zp2 to Zp9.

Since a traveling direction of a laser light is changed by the scanner30 over time, as shown in FIG. 4, the laser lights (laser beams) scanthe light diffusion devices 50 a, 50 b and 50 c along the longitudinaldirections of the light diffusion devices 50 a, 50 b and 50 c. As shownin FIG. 4, an area on the light diffusion device 50 irradiated with thelaser light at a certain instance, i.e., a spot area S has a planardimension smaller than the element diffusion device 55. The spot area Sscans the first to ninth element diffusion devices 55 a to 55 isequentially.

The light diffusion device 50 is formed with the use of a hologramstorage medium 52, for example. In the example shown in FIGS. 1 and 4,three hologram storage media 52 a, 52 b and 52 c are disposedcorrespondingly to the respective light diffusion devices 50 a, 50 b and50 c. The respective hologram storage media 52 a, 52 b and 52 c areprovided correspondingly to laser lights of different wavelength ranges.By using laser lights of different wavelength ranges which have enteredthe whole area of the respective hologram storage media 52 a, 52 b and52 c so as to be diffused, the whole area of the common illuminationarea Z can be illuminated.

Each of the hologram storage media 52 a, 52 b and 52 c is segmented intoa plurality of the element diffusion devices 55. The respective elementdiffusion devices 55 are formed of element holograms 57 storinginterference fringe patters different from one another. A laser lightincident on each element hologram 57 is diffracted by an interferencefringe pattern, and illuminates a corresponding element illuminationarea Zp in the illumination area Z. By variously adjusting theinterference fringe patterns, a traveling direction of a laser lightthat is diffracted by each element hologram 57, in other words, atraveling direction of a laser light that is diffused by each elementhologram 57 can be controlled.

The element hologram 57 can be manufactured by using scattered lightfrom a real scattering plate as object light, for example. To be morespecific, when a hologram photosensitive material that is a matrix ofthe element hologram 57 is irradiated with reference light and objectlight of coherent light interfering with each other, interferencefringes by the light interference are formed on the hologramphotosensitive material so that the element hologram 57 is manufactured.Laser light that is coherent light is used as reference light, whilescattered light of an isotropic scattering plate, which is availableinexpensively, is used as object light, for example.

By emitting laser light toward the element diffusion device 55 such thatthe laser light travels reversely to the light path of the referencelight that was used when the element hologram 57 was manufactured, areconstructed image of the scattering plate is generated on a positionwhere the scattering plate is located, from which the object light usedwhen the element hologram 57 was manufactured was generated. When thescattering plate from which the object light used when the elementhologram 57 was manufactured was generated uniformly scattered light byits surface, the reconstructed image of the scattering plate obtained bythe hologram 57 is a uniform surface illumination. Thus, an area inwhich the reconstructed image of the scattering plate is generatedbecomes an element illumination area Zp.

Instead of being formed by using real object light and reference light,a complicated interference fringe pattern formed on each elementhologram 57 can be designed by using a computer based on a wavelengthand an incident direction of expected illumination light to bereconstructed as well as a shape and a position of an image to bereconstructed. An element hologram 57 thus obtained is also referred toas computer generated hologram (CGH). In addition, a Fourier conversionhologram in which respective points on each element hologram 57 have thesame diffusion angle properties may be generated by a computer. Further,a size and a position of an actual illumination range may be set bydisposing an optical member such as a lens behind an optical axis of anelement illumination area Zp.

One of the advantages of providing the element hologram 57 as theelement diffusion device 55 is that a light energy density of laserlight can be decreased by diffusion. Another advantage is that theelement hologram 57 can be used as a directional surface light source.In this case, as compared with a conventional lamp light source (pointlight source), a luminance on a light source surface for achieving thesame illumination distribution can be decreased. Thus, safety of laserlight can be improved. Namely, even when a person looks a laser lighthaving passed through the element illumination area Zp with his/hereyes, the eyes are less affected as compared with a case in which aperson looks a single point light source with his/her eyes.

Specifically, the element diffusion device 55 may be a volume typehologram storage medium using a photopolymer, a volume type hologramstorage medium that stores hologram using a photosensitive mediumcontaining a silver salt material, or a relief type (embossing type)hologram storage medium.

Next, an operation of the illumination device 10 as structured above isdescribed.

As shown in FIG. 1, based on a control signal from the emission controlunit 12, the respective light source units 17 a, 17 b and 17 c oscillatelaser lights (laser beams) of respective wavelength ranges. Laser lightsgoing out from the laser light source 15 firstly travel toward theshaping optical system 20. In the example shown in FIG. 2, the laserlights of the respective wavelength ranges are shaped into parallellight fluxes lf1 by the beam expander 21 and the collimation lens 22 ofthe shaping optical system 20. Thereafter, each of the parallel lightfluxes lf1 of the respective wavelength ranges is divided intoconvergent light fluxes lf2 by the element lens 24 of the lens array 23.As to the laser lights of the respective wavelength ranges, theconvergent light fluxes lf2 are similarly shaped, and optical axesd_(lf2) of the convergent light fluxes lf2 are parallel to one another.

The laser lights having been shaped by the shaping optical system 20,i.e., the convergent light fluxes lf2 travel toward the polygonal mirror31 forming the scanner 30. The polygonal mirror 31 is consecutivelyrotated about the rotational axis line ra. Thus, an inclination angle ofthe reflection surface of the polygonal mirror 31 is cyclically changedwithin a predetermined angular area. As a result, a direction of a laserlight reflected by the polygonal mirror 31 cyclically changes.

As shown in FIG. 2, the polygonal mirror 31 reflects the convergentlight fluxes lf2 on a position where the convergent light fluxes lf2converge, or on a position close thereto. Thus, since the convergentlight fluxes lf2 are reflected by the polygonal mirror 31, theconvergent light fluxes lf2 are converted into divergent light fluxeslf3 whose divergent points are located on the reflection position of thepolygonal mirror 31, or on a position close thereto. Each of the sixreflection surfaces of the polygonal mirror 31 is large enough toreflect all the convergent light fluxes lf2 having been shaped by theshaping optical system 20. Thus, as shown in FIG. 3, optical axesd_(lf3) of the divergent light fluxes lf3 that are the laser lightsreflected by the polygonal mirror 31 remain parallel. Since thepolygonal mirror 31 reflects the light fluxes lf3 that are in theconvergent state, enlargement of the polygonal mirror 31 can beeffectively avoided.

In addition, the polygonal mirror 31 includes the first reflection unit31 a, the second reflection unit 31 b and the third reflection unit 31c, along this rotational axis line ra. Since these reflection units 31a, 31 b and 31 c are synchronically operated, the laser light from thefirst light source unit 17 a, the laser light from the second lightsource unit 17 b and the laser light from the third light source unit 17c synchronically change their traveling directions.

As shown in FIG. 3, the divergent light fluxes lf3 with their lightpaths having been adjusted by the scanner 30 enter the light condensingoptical system 40. The optical axes d_(lf3) of the divergent lightfluxes lf3 remain parallel to one another. In addition, the lightdiffusion device 50 is located on the focus Pf of the light condensinglens 41 forming the light condensing optical system 40. Thus, lightfluxes lf4 with their light paths having been adjusted by the lightcondensing lens 41 are condensed by the light condensing lens 41, andtheir optical axes d_(lf4) intersect on the light diffusion device 50.In particular, in the illustrated example, the reflection position ofthe polygonal mirror 31 is located on a focus position behind the lightcondensing lens 41, or on a position close thereto. Thus, the lightfluxes lf3 traveling from the polygonal mirror 31 toward the lightcondensing lens 41 are converted to parallel light fluxes lf4 by thelens effect of the light condensing lens 41. The parallel light fluxeslf4 are overlapped with one another on the light diffusion device 50.

An area on which the parallel light fluxes lf4 are overlapped with oneanother on the light diffusion device 50, i.e., the spot area S scansthe light diffusion device 50 along the longitudinal direction of theelongate light diffusion device 50, in conjunction with the operation ofthe scanner 30. As a result, as shown in FIG. 4, the laser lightssequentially irradiate the element diffusion devices 55. The laser lightincident on each element diffusion device 55 is diffused by the elementdiffusion device 55 so as to illuminate the whole area of an elementillumination area Zp corresponding to the element diffusion device 55.

The emission control unit 12 controls emission of laser lights from thelight source unit 17, depending on irradiation positions of laser lightson the light diffusion device 50. Thus, only a desired elementillumination area Zp in the illumination area Z can be selected andilluminated. In addition, the emission control unit 12 can controlemission of light from the light source units 17 a, 17 b and 17 cindependently. Thus, it is also possible to illuminate a predeterminedelement illumination area Zp with light emitted from one(s) selectedfrom the first light source unit 17 a, the second light source unit 17 band the third light source unit 17 c. That is to say, each of the firstto ninth element illumination areas Zp1 to Zp9 included in theillumination area Z can be adjusted independently from the other elementillumination areas, as to whether illuminated or not, the degree ofbrightness and the color of illumination light.

As disclosed in WO2012/033174A, the use of coherent light gives rise togeneration of speckles. The speckles may be recognized as a spot patternto cause physiological discomfort.

In the illustrated illumination device 10, as shown in FIG. 4, an areaon the light diffusion device 50 irradiated with a laser light at acertain instance, i.e., a spot area S, which is irradiated withoverlapped parallel light fluxes lf4, is smaller than the element lightdiffusion device 55. The spot area S moves in the element diffusiondevice 55 in conjunction with the operation of the scanner 30. Theelement diffusion device 55 is formed of the element hologram 57 as thehologram storage medium 52, for example, and diffuses light of apredetermined wavelength range, which has entered a given part thereoffrom a predetermined direction or a direction close thereto, so as toilluminate the whole area of an element illumination area Zpcorresponding to the element diffusion device 55. Thus, while a spotarea S moves in one element diffusion device 55, an incident directionof illumination light incident on each position of the elementillumination area Zp changes over time. The fast change of incidentdirection cannot be dissolved by human eyes, whereby multiplexedcoherent light scattered patterns that are not correlated to one anotherare observed by the human eyes. Therefore, speckles generatedcorrespondingly to the respective scattered patterns are overlapped andaveraged, which is observed by an observer. For this reason, thespeckles can be made unnoticeable in each element illumination area Zp.

In order to simplify control of the scanner 30, the scanner 30 ispreferably operated such that a laser light can cyclically scan thewhole area of the light diffusion device 50. In the example shown inFIG. 4, the scanner 30 is preferably operated such that a laser lightscans over the whole lengths of the light diffusion devices 50 a, 50 band 50 c along the longitudinal directions of the light diffusiondevices 50 a, 50 b and 50 c. When only a predetermined elementillumination area Zp is desired to be illuminated, the emission controlunit 12 controls emission or stop of laser light of the laser lightsource 15, depending on the operation of the scanner 30, in other words,depending on a position on the light diffusion device 50 to beirradiated with a laser light.

On the other hand, coherent light emitted from a coherent light sourcesuch as a laser light source generally involves illuminancenon-uniformity in a spot area. Generally, as shown in FIG. 6, the centerof the spot area Sp is brightest, and it gradually darkens toward aperiphery of the spot area Sp. Typically, an illuminance distribution isthe Gaussian distribution from the center of the spot area Sp toward theperiphery thereof. Namely, the spot area Sp has a large rim part of alow illuminance. Thus, as shown in FIG. 6, an effective scanning sectionscp1, in which the whole spot area Sp is located inside one elementdiffusion device 55 corresponding to a predetermined elementillumination area Zp, is relatively short. On the other hand, as shownin FIG. 6, an ineffective scanning section scp2, in which only a part ofthe spot area Sp is located within the one element diffusion device 55,i.e., in the example shown in FIG. 6, the ineffective scanning sectionscp2, in which the spot area Sp is located over two element diffusiondevices 55 that are adjacent in a scanning direction sd, is relativelylong. In the example shown in FIG. 6, the effective scanning sectionscp1 is significantly shorter than the ineffective scanning sectionscp2.

In the example shown in FIG. 6, when only a predetermined elementillumination area Zp is illuminated, the emission control unit 12 emitsa laser light in such a manner that the center of the spot area Sp islocated within the effective scanning section scp1, while stops emissionof laser light in such a manner that the center of the spot area Sp islocated within the ineffective scanning section scp2. Thus, when thescanner 30 is operated at a constant speed, in the example shown in FIG.6, a time period in which the emission of laser light is stopped issignificantly long. Namely, the laser light source 15 is not efficientlyused. Further, in order to illuminate an element illumination area Zpsufficiently brightly by emitting light in a short period of time, it isnecessary to prepare a high output laser light source.

In order to deal with this problem, the illumination device 10 in thefirst embodiment is equipped with the shaping optical system 20 and thescanner 30. The shaping optical system 20 shapes coherent light emittedfrom the laser light source 15. The light condensing optical system 40is located on a light path of coherent light from the shaping opticalsystem 20 up to the light diffusion device 50, and condenses thecoherent light such that the spot area S on the light diffusion device50 is smaller than the element diffusion device 55. Due to the shapingoptical system 20 and the scanner 30, it is possible not only toregulate the shape and the size of the spot area S on the lightdiffusion device 50, but also to make uniform an illuminancedistribution of the spot area S.

Thus, as shown in FIG. 5, the effective scanning section sc1, in whichthe whole spot area S is located only within one element diffusiondevice 55 corresponding to a predetermined element illumination area Zp,can be made relatively long. On the other hand, as shown in FIG. 5, theineffective scanning section scp2, in which only a part of the spot areaS is located within the one element diffusion device 55, i.e., in theillustrated example, the ineffective scanning section scp2, in which thespot area Sp is located over two element diffusion devices 55 that areadjacent in the scanning direction sd, can be made relatively short. Inthe example shown in FIG. 5, the effective scanning section sc1 issignificantly longer than the ineffective scanning section sc2. Thus,even when only a predetermined element illumination area Zp isilluminated, a period of time in which a laser light is emitted can beincreased. Thus, it is possible to illuminate the element diffusiondevice 55 sufficiently brightly by means of the efficient use of thelaser light source 15, instead of using a high output laser light source15. Thus, the performance of the laser light source 15 is sufficientlyutilized so as to illuminate the illumination area Z in a desired lightdistribution pattern with a sufficiently bright quantity of light.

Particularly in the example shown in FIGS. 4 and 5, a size wsx of thespot area S along a direction parallel to the scanning direction sd ofthe spot area S is significantly smaller than a size wsy of the spotarea S along a direction orthogonal to the scanning direction sd of thespot area S, in particular, smaller than a half of the size wsy. In thedirection parallel to the scanning direction sd of the spot area S, thesize wsx of the spot area S is significantly smaller than a size wpx ofthe element diffusion device 55, in particular, smaller than a half ofthe size wpx. Thus, the ineffective scanning section sc2, in which onlya part of the spot area S is located within the one element diffusiondevice 55, can be made very short. Therefore, according to the exampleshown in FIGS. 4 and 5, a period of time in which the laser light source15 stops emission of laser light can be significantly made short. Thatis to say, the laser light source 15 can be more efficiently utilized.

In addition, as shown in FIG. 5, in the direction orthogonal to thescanning direction sd of the spot area S, the size wsy of the spot areaS is substantially the same as or slightly smaller than the size wpy ofthe element diffusion device 55. Thus, most of the light diffusiondevice 50 can be irradiated with coherent light, in conjunction with theoperation of the scanner 30. Namely, the whole surface of the lightdiffusion device 50 can be efficiently utilized, so as to avoidenlargement of the illumination device 10.

Further, adjustment of the shape of the spot area S and the illuminancedistribution in the spot area S by using the shaping optical system 20and the light condensing optical system 40 is advantageous in terms ofmaking speckles unnoticeable.

As shown in FIG. 5, by making smaller the size wsx of the spot area Salong the direction parallel to the scanning direction sd of the spotarea S, a period of time in which respective positions of the elementdiffusion device 55 is irradiated with coherent light can be maderelatively short. That is to say, a position from which illuminationlight toward each position of the element illumination area Zp goes outswitches for a short period of time. In other words, an incidentdirection of the illumination light toward each position of the elementillumination area Zp change rapidly. As a result, since speckle patternsare overlapped over time, speckles can be effectively made unnoticeable.

In addition, as shown in FIG. 5, by making uniform the illuminancedistribution in the spot area S, speckles can be effectively madeunnoticeable at each instance. As shown in FIG. 6, when the uniformityof illumination distribution in the spot area Sp is low, a phaseintensity from each position in the spot area Sp toward one position Psin the element illumination area Zp at a given instance becomesnon-uniform. Thus, since the overlap of speckle patterns at eachinstance is insufficient, the speckle reduction effect cannot beefficiently exerted in a sufficient manner. On the other hand, as shownin FIG. 5, when the illumination distribution in the spot area Sp isuniform, a phase intensity from each position in the spot area S towardone position Ps in the element illumination area Zp at a given instancecan be made uniform. Thus, since the overlap of speckle patterns at eachinstance is effectively realized, the speckle reduction effect can beefficiently exerted in a sufficient manner.

Particularly in the example shown in FIG. 5, the large size wsy of thespot area S in the direction orthogonal to the scanning direction sd ofthe spot area S is ensured. Thus, while the size wsx of the spot area Sin the direction parallel to the scanning direction sd of the spot areaS is small, broadness of the spot area S can be effectively ensured. Asa result, the overlap of speckle patterns can be more effectivelyrealized at each instance.

As described above, in the first embodiment, the illumination device 10includes the shaping optical system 20 that shapes coherent light, andthe light condensing optical system 40 located on a light path of thecoherent light from the shaping optical system 20 up to the lightdiffusion device 50. The light condensing optical system 40 condensescoherent light such that the spot area S on the light diffusion device50 is smaller than the element diffusion device 55. Each elementdiffusion device 55 diffuses coherent light incident thereon so as toilluminate an element illumination area Zp corresponding to the elementdiffusion device 55. According to the first embodiment, the shape of thespot area S and the illuminance distribution of the spot area S can beadjusted by the shaping optical system 20 and the light condensingoptical system 40. As a result, the performance of the laser lightsource 15 is sufficiently utilized so as to illuminate the illuminationarea Z in a desired light distribution pattern with a sufficientlybright quantity of light.

In addition, in the first embodiment, the shaping optical system 20divides coherent light emitted from the coherent light source 15 intolight fluxes lf2. The light condensing optical system 40 adjusts lightpaths of light fluxes lf3 such that the light fluxes f13 are at leastpartially overlapped on the light diffusion device 50. Thus, even whenan illuminance distribution of the coherent light upon emission from thecoherent light source 15 is non-uniform, since the illuminancedistribution is divided and overlapped, the illuminance distribution canbe effectively made uniform. In particular, when the illuminancedistribution of the coherent light upon emission from the coherent lightsource 15 is the typical Gaussian distribution, the illuminancedistribution is planarly divided and overlapped, so that the illuminancedistribution can be significantly effectively made uniform. Thus, theillumination area Z can be more brightly illuminated with a desiredlight distribution pattern.

Further, in the first embodiment, the light condensing optical system 40is the lens 41 having the focus position Pf on which the light diffusiondevice 50 is located. According to such a light condensing opticalsystem 40, although it has a simple structure, light incident on thelight condensing optical system 40 at a given instance can be condensedhighly efficiently on the spot area S on the light condensing opticalsystem 40, so that the illuminance distribution of the spot area S canbe effectively made uniform.

Further, in the first embodiment, the shaping optical system 20 includesthe collimation lens 22, and the lens array 23 located on a light pathfrom the collimation lens 22 up to the light condensing optical system40. According to such a shaping optical system 20, the optical axesd_(lf3) of the light fluxes lf3 incident on the light condensing opticalsystem 40 can be made parallel. In this case, by means of the lightcondensing optical system 40 using the light condensing lens 41, theoptical axes d_(lf4) of the light fluxes, which have been shaped by theshaping optical system 20, can be allowed to intersect on the lightdiffusion device 50. Thus, the illuminance distribution of the spot areaS can be more effectively made uniform.

Further, in the first embodiment, the lens array 23 includes the elementlenses 24. The light fluxes lf2 emergent from the element lenses 24 canbe the same light distributions each other. In this case, by means ofthe light condensing optical system 40 using the light condensing lens41, the light fluxes which have been shaped by the shaping opticalsystem 20 can be highly precisely overlapped with one another on thelight diffusion device 50. Thus, the shape of the spot area S can bemore precisely adjusted, and the illuminance distribution of the spotarea S can be more effectively made uniform.

The aforementioned first embodiment can be variously modified.Modification examples are described herebelow. In the drawings used inthe below description, a component that can be similarly structured asthat of the above embodiment has the same reference number as the numberused for the corresponding component of the above embodiment, andredundant description is omitted.

In the aforementioned first embodiment, there is shown the example inwhich the shaping optical system 20 includes the beam expander 21, thecollimation lens 22 and the lens array 23. However, the presentinvention is not limited to this example. The shaping optical system 20may be made of a beam homogenizer 25 that forms a uniform intensitydistribution. As the beam homogenizer 25, a member using diffractiveoptical elements (DOE) or a member using an aspherical lens or afree-form surface lens can be employed.

In addition, in the aforementioned first embodiment, there is shown theexample in which the light diffusion device 50 is made of the hologramstorage medium 52. However, the present invention is not limited to thisexample. For example, the light diffusion device 50 may be made by usinga lens array group in which the respective element diffusion devices 55constitute one lens array. In this case, the lens array is provided foreach element distribution device 55, and the shape of each lens array isdesigned such that each lens array illuminates an element illuminationarea Zp in the illumination area Z. Positions of the respective elementillumination areas Zp are at least partially different.

Further, in the aforementioned first embodiment, there is shown theexample in which the polygonal mirror 31 reflects a laser light on aposition apart from the element lens 24 by the focus distance of theelement lens 24 along the optical axis d₂₄ of the element lens 24.However, the present invention is not limited to this example. Inaddition, in the aforementioned first embodiment, there is shown theexample in which the polygonal mirror 31 reflects a laser light on aposition apart from the light condensing lens 41 by the focus distanceof the light condensing lens 41 along the optical axes d₄₀ of the lightcondensing lens 41. However, the present invention is not limited tothis example. For example, the light condensing lens 41 may be locatedon a light path from the element lens 24 toward the scanner 30. Inaddition, the lens array 23 including the element lenses 24 may belocated on a light path from the scanner 30 toward the light condensingoptical system 40.

Further, in the aforementioned first embodiment, there is shown theexample in which the laser light source 15 as a coherent light sourceemits laser lights of different wavelength ranges. However, the presentinvention is not limited to this example. The coherent light source maybe made as a light source that emits coherent light of the samewavelength range.

Further, the above-described illumination device 10 may be mounted on aconveyance, or installed at a predetermined location. When it is mountedon a conveyance, the conveyance may be various moving bodies such as avehicle like an automobile, a flying body like an aircraft, a train, aship, a diving body and so on.

Although some modification examples of the first embodiment have beendescribed above, the modification examples can be naturally combined andused.

Next, a second embodiment is described with reference to an exampleshown in FIGS. 7 to 13.

FIG. 7 is a perspective view schematically showing an overall structureof an illumination device 110. The illumination device 110 illuminatesan illumination area Z using coherent light such as laser light (laserbeam). The illumination device 110 includes, as a light source, a laserlight source 115 that oscillates laser light. The laser light source 115oscillates laser light that is coherent light. The illumination device110 includes a diffusion optical system 120, a scanner 130, a lightcondensing optical system 140 and a light deflection device 150, whichprocess light emitted from the laser light source 115. In the exampleshown in FIG. 7, the diffusion optical system 120, the scanner 130, thelight condensing optical system 140 and the light deflection device 150are located in this order along a light path of laser light from thelaser light source 115, and they process laser light in this order. Asdescribed in detail below, the illumination device 110 described hereincan illuminate, with a large quantity of light, the illumination area Zin a desired light distribution pattern, while sufficiently utilizingthe performance of the light source 115 by means of optical actions inthe diffusion optical system 120 and the light condensing optical system140. Herebelow the respective constituent elements are sequentiallydescribed.

In the example shown in FIG. 7, the laser light unit 115 includes aplurality of light source units 117 that emit laser light. The lightsource units 117 may be independently arranged, or may be a light sourcemodule formed by arranging the light source units 117 side by side on acommon substrate. For example, the light source units 117 have a firstlight source unit 117 a that oscillates light of a red emissionwavelength range, a second light source unit 117 b that oscillates lightof a green emission wavelength range, and a third light source unit 117c that oscillates light of a blue emission wavelength range. Accordingto this example, since three laser lights (laser beams) emitted from thelight source units 117 a, 117 b and 117 c are overlapped, illuminationbeams of various colors including a white illumination beam can begenerated.

Although an example in which the laser light source 115 has the threelight source units 117 a, 117 b and 117 c having emission wavelengthranges different from one another is described herebelow, the presentinvention is not limited thereto. The laser light source 115 may havetwo light units 117 having emission wavelength ranges different fromeach other, or four or more light units 117 having emission wavelengthranges different from one another. In addition, in order to increaseemission intensity, a plurality of the light source units 117 may beprovided for each emission wavelength range.

As shown in FIG. 7, the illumination device 110 includes an emissioncontrol unit 112 connected to the laser light source 115. The emissioncontrol unit 112 controls emission timings of laser lights (laser beams)emitted by the laser light source 115. In particular, the emissioncontrol unit 112 can switch emission of laser lights and stop ofemission of laser lights from the light source unit 117 a, 117 b or 117c, independently from other light source units. The control of emittingor not emitting laser lights by the emission control unit 112 is carriedout based on scanning timings of a plurality of laser lights by thescanner 130, in other words, based on incident positions of laser lightson the light deflection device 150. As described above, in the casewhere the laser light source 115 can emit three laser lights, i.e., ared laser light, a blue laser light and a green laser light, it ispossible to generate illumination light of a color that is a combinationof given two or more colors of red, blue and green, by controlling anemission timing of each laser light.

The emission control unit 112 may control whether a laser light isemitted from each light source unit 117 or not, i.e., ON/OFF ofemission, or may switch blocking or not blocking of a light path of alaser light having been emitted from each light source unit 117. In thelatter case, light shutter units, not shown, may be disposed between therespective light source units 117 and the diffusion optical system 120,such that passage and blockage of laser lights can be switched by thelight shutter units.

Next, the diffusion optical system 120 is described. The diffusionoptical system 120 diffuses laser light emitted from the laser lightsource 115. In particular, the diffusion optical system 120 diffuseslight from the light source (light-source light) such that across-sectional area of the light immediately before it enters the lightcondensing optical system 140 is larger than a cross-sectional area ofthe light immediately before it enters the diffusion optical system 120.The cross-sectional area of light is an area occupied by a light path ina cross-section orthogonal to an optical axis of the light. In addition,an optical axis is an axis line in which an intensity of the light ishighest. Thus, the diffusion optical system 120 shapes, for example,incident light into a divergent light flux or a convergent light flux.

FIG. 8 is a plan view showing the illumination device 110. As shown inFIG. 8, the diffusion optical system 120 includes a beam expander 121, acollimation lens 122 and a lens array 123, in this order along a lightpath of laser light. The beam expander 121 shapes a laser light emittedfrom the laser light source 115 into a divergent light flux. Thecollimation lens 122 reshapes the divergent light flux generated by thebeam expander 121 into parallel light fluxes lf11. The lens array 123includes a plurality of element lenses 124 that are arranged onpositions facing the collimation lens 122. The element lenses 124 arepositioned such that an optical axis d₁₂₄ of each element lens 124 isparallel to an optical axis d₁₂₂ of the collimation lens 122. Inaddition, the element lenses 124 are arranged on a virtual face vl thatis orthogonal to the optical axis d₁₂₂ of the collimation lens 122. Eachelement lens 124 shapes a parallel light flux lf11, which has beenshaped by the collimation lens 122 and has entered the element lens 124,into a convergent light flux lf12.

In the example shown in FIG. 8, the diffusion optical system 120 dividesa laser light emitted from the laser light source 115 into a pluralityof light fluxes lf12. The diffusion optical system 120 divides a laserlight into light fluxes lf12 the number of which is equal to the numberof the element lenses 124 included in the lens array 123. In theillustrated example, each element lens 124 shapes a parallel light fluxlf11, which has been shaped by the collimation lens 122 and has enteredthe element lens 124, into a convergent light flux lf12. That is to say,respective light fluxes lf12 divided by the diffusion optical system 120are convergent light fluxes. In addition, in the illustrated example,the element lenses 124 have the same structures each other. Thus, lightfluxes f112 emitted from the element lenses 124 are the same lightdistributions. For example, the light fluxes lf12 have the sameconvergent angles and the same convergent positions, and optical axesd_(lf12) of the light fluxes lf12 are parallel to one another.

A plurality of the diffusion optical systems 120 may be providedcorrespondingly to the respective light source units 117 included in thelaser light source 115. Alternatively, the single diffusion shapingoptical system 120 capable of adjusting light paths of laser lights fromthe light source units 117 a, 117 b and 117 c may be provided. In theexample shown in FIG. 8, the light source units 117 a, 117 b and 117 cmay be aligned in the depth direction of the sheet plane of FIG. 8, thebeam expander 121 may diverge a laser light only in a plane of the sheetplane of FIG. 8, and the collimation lens 122 and the element lenses 124of the lens array 123 in the diffusion optical system 120 mayrespectively be formed as cylindrical lenses extending to have a certaincross-sectional shape in the depth direction of the sheet plane of FIG.8. According to this example, the light source units 117 can share thecollimation lens 122 and the lens array 123.

Next, the scanner 130 is described. The scanner 130 adjusts a travelingdirection of a laser light emitted from the laser light source 115. Thescanner 130 changes traveling directions of laser lights with time. Dueto the light path adjustment of the scanner 130, a laser light emittedfrom the laser light source 115 scans the light deflection device 150.In the example shown in FIGS. 7 and 8, the scanner 130 is formed as apolygonal mirror 131 having six reflection surfaces. When the polygonalmirror 131 is rotated about its central axis line as a rotational axisline ra, a reflection direction of light that has entered there from acertain direction can be changed cyclically. The respective sixreflection surfaces of the polygonal mirror 131 are formed as flatsurfaces. Thus, as shown in FIG. 9, after three light fluxes lf13, whichhad been shaped by the diffusion optical system 120, have been reflectedby the polygonal mirror 131 so that their traveling directions have beenchanged, optical axes d_(lf13) of the light fluxes lf13 remain parallel.FIG. 9 is a partially enlarged plan view showing a light path succeedingto the scanner 130.

In particular, in the illustrated example, the light source units 117 a,117 b and 117 c are aligned in a direction parallel to the rotationalaxis line ra of the polygonal mirror 131 (see FIG. 7). The reflectionsurface of the polygonal mirror 131 includes, along this rotational axisline ra, a first reflection unit 131 a, a second reflection unit 131 band a third reflection unit 131 c. The first reflection unit 131 areflects a laser light emitted from the first light source unit 117 aand cyclically changes a traveling direction of the laser light in aplane orthogonal to the rotational axis line ra. In addition, the secondreflection unit 131 b reflects a laser light emitted from the secondlight source unit 117 b, and the third reflection unit 131 c reflects alaser light emitted from the third light source unit 117 c.

As shown in FIG. 8, the polygonal mirror 131 is positioned with respectto the diffusion optical system 120, such that the polygonal mirror 131reflects light from the diffusion optical system 120 on a focus positionof each element lens 124 of the lens array 123, or on a position closethereto. Thus, as shown in FIG. 9, light reflected from the polygonalmirror 131 substantially becomes a divergent light flux lf13 whosedivergent point is the reflection surface of the polygonal mirror 131.

The scanner 130 is not limited to the illustrated polygonal mirror 131.It is possible to use, as the scanner 130, an apparatus thatthree-dimensionally changes in a biaxial direction a traveling directionof light incident thereon from a certain direction. For example, MEMS(micro electromechanical systems) such as a digital micromirror device(DMD) may be used as the scanner 130.

Next, the light condensing optical system 140 is described. The lightcondensing optical system 140 is located on a light path of a laserlight from the diffusion optical system 120 up to the light deflectiondevice 150. The light condensing optical system 140 optically processesa laser light diffused by the diffusion optical system 120. The lightcondensing optical system 140 condenses an expanded laser light suchthat a spot area S on the light deflection device 150, i.e., an area,which is irradiated with a laser light on the light deflection device150 at a given instance, has a smaller planar dimension.

In the illustrated example, the light condensing optical system 140 isformed by a light condensing lens 141 having a focus Pf. The lightcondensing lens 141 is located on a light path of a laser light from thescanner 130 toward the light deflection device 150. As described above,the diffusion optical system 120 divides a laser light into light fluxeslf13. As shown in FIG. 9, the optical axes d_(lf13) of the light fluxeslf13 are parallel to one another. Thus, as shown in FIG. 9, because of alens action of the light condensing lens 141, optical axes d_(lf14) ofthree light fluxes lf14 intersect on a position Px on a virtual face vlfthat is apart from the light condensing lens 141 by a focus distancef₁₄₀ of the light condensing lens 141 along an optical axis d₁₄₀ of thelight condensing lens 141. In the illustrated example, the lightdeflection device 150 is located on the virtual face vlf that is apartfrom the light condensing lens 141 by the focus distance f₁₄₀ of thelight condensing lens 141 along the optical axis d₁₄₀ of the lightcondensing lens 141. Thus, the three light fluxes lf13 having beenshaped by the diffusion optical system 120 are overlapped at leastpartially on the light deflection device 150, by the light condensingaction of the light condensing optical system 140.

A convergent angle θ_(x) of the optical axis d_(lf14) of the convergentlight flux lf14 in FIG. 9 depends on a light path width of the overalllight-source light before it enters the light condensing lens 141. Thelight path width of the light-source light can be adjusted by a widthw_(lf11) (see FIG. 8) of the parallel light flux lf11 formed by the beamexpander 121 and the collimation lens 122 of the diffusion opticalsystem 120. Thus, by suitably designing the beam expander 121 and thecollimation lens 122, the convergent angle θ_(x) of the optical axisd_(lf14) of the convergent light fluxes lf14 can be adjusted when thelight fluxes lf14 enter a spot area S.

In particular, in the illustrated example, as shown in FIG. 9, thescanner 130 and the light condensing optical system 140 are located suchthat the polygonal mirror 131 reflects a laser light from the diffusionoptical system 120 on a position apart from the light condensing lens141 by the focus distance f₁₄₀ of the light condensing lens 141 alongthe optical axis d₁₄₀ of the light condensing lens 141, or on a positionclose to the position. Further, as described above, each of light fluxeslf13, which has been reflected by the polygonal mirror 131 and hasentered the light condensing optical system 140, is a divergent lightflux lf13 whose divergent point is located on the reflection surface ofthe polygonal mirror 131, or close thereto. Thus, each light flux lf13incident on the light condensing lens 141 passes through the lightcondensing lens 141 so as to be converted to a parallel flux lf14. As aresult, the light fluxes lf14 having been shaped by the diffusionoptical system 120 irradiate the same area on the light deflectiondevice 150 by the light condensing function of the light condensingoptical system 140, i.e., the light fluxes lf14 are overlapped on thelight deflection device 150 highly precisely. Since the scanner 130changes traveling directions of laser lights over time, a spot area S onwhich the light fluxes lf14 are condensed by the light condensingoptical system 140 changes its position over time on the lightdeflection device 150.

A width wsx of the spot area S in FIG. 9 depends on a distance betweenthe light condensing optical system 140 and the scanner 130, and adivergent angle θ_(lf13) of a divergent light flux lf13 that enters thelight condensing optical system 140. In addition, the divergent angleθ_(lf13) of the divergent light flux lf13 depends on a convergent angleθ_(lf12) of the convergent light flux lf12 having been shaped by theelement lens 124 of the diffusion optical system 120. Thus, by suitablypositioning the light condensing optical system 140 and the scanner 130and by suitably designing the element lens 124, the width wsx of thespot area S can be adjusted. In particular, by suitably designing theelement lens 124, the width wsx of the spot area S can be adjusted whileeffectively avoiding enlargement of the illumination device 110.

A plurality of the light condensing optical systems 140 may be providedcorrespondingly to the respective light source units 117 a, 117 b and117 c included in the laser light source 115. Alternatively, the singlelight condensing optical system 140 capable of adjusting light paths oflaser lights from the light source units 117 a, 117 b and 117 c may beprovided. For example, when a laser light is diverged or converged onlyin a plane parallel to the sheet plane of FIG. 9, the light condensinglens 141 forming the light condensing optical system 140 may be acylindrical lens extending to have a certain cross-sectional shape inthe depth direction of the sheet plane of FIG. 8. According to thisexample, the light condensing lens 141 can be shared by laser lightsemitted by the light source units 117 a, 117 b and 117 c.

Next, the light deflection device 150 is described. The light deflectiondevice 150 adjusts a light path of light from the light source unit 115to direct the incident light to a predetermined range so as toilluminate the predetermined range. To be more specific, a laser lightwhose light path is adjusted by the light deflection device 150 passesthrough an illumination area Z, and then illuminates a predeterminedrange that is an actual illumination range.

The illumination area Z and an element illumination area Zp (see FIG.11), which forms a part of the illumination area Z, are illuminationareas of near fields that are overlappingly illuminated by respectiveelement deflection devices 155 in the light deflection device 150. Anillumination range of a far field is generally expressed as a diffusionangle distribution in an angular space, rather than an actualillumination area size. The terms “illumination area” and “elementillumination area” in this specification include a diffusion angle rangein an angular space in addition to an actual illumination area(illumination range). Thus, a predetermined range illuminated by theillumination device 110 of FIGS. 7 and 10 can be an area that is greatlylarger than the illumination area Z of a near field shown in FIGS. 7 and10.

FIG. 10 is a plan view showing the light deflection device 150. In theillustrated example, the light deflection device 150 includes the firstlight deflection device 150 a, a second light deflection device 150 band a third light deflection device 150 c, correspondingly to the factthat the laser light source 115 includes the first to third light sourceunits 117 a, 117 b and 117 c. A laser light from the first light sourceunit 117 a enters the first light deflection device 150 a, a laser lightfrom the second light source unit 117 b enters the second lightdeflection device 150 b, and a laser light from the third light sourceunit 117 c enters the third light deflection device 150 c. By using thelaser lights that have entered the whole areas of the respective lightdeflection devices 150 a, 150 b and 150 c so that their light paths areadjusted, the whole area of the common illumination area Z can beilluminated.

Thus, the first light deflection device 150 a directs red light from thefirst light source unit 117 a toward the illumination area Z, the seconddeflection device 150 b directs green light from the second light sourceunit 117 b toward the illumination area Z and the third light deflectiondevice 150 c directs blue light from the third light source unit 117 ctoward the illumination area Z, whereby the illumination area Z can beilluminated in white. As shown in FIG. 7, the light deflection devices150 a, 150 b and 150 c are respectively formed to have an elongate shapein a direction orthogonal to the rotational axis line ra of thepolygonal mirror 131 forming the scanner 130. The light deflectiondevices 150 a, 150 b and 150 c are arranged side by side in a directionorthogonal to their longitudinal directions.

As shown by the dotted lines in FIG. 10, each of the light deflectiondevices 150 a, 150 b and 150 c has a plurality of element deflectiondevices 155. Each element deflection device 155 has a light path controlfunction for directing a traveling direction of light, which has beenincident thereon from a certain direction, toward a predetermineddirection. For example, when lights enter one element deflection device155 from two different directions, the lights from the respectivedirections go out from the element deflection device 155 towarddirections different from each other. In addition, each elementdeflection device 155 has a light path control function different fromthe other element deflection devices 155. Thus, lights, whichrespectively have entered two different element deflection devices 155from the same direction, go out from the element deflection devices 155toward directions different from each other.

In the illustrated example, when light has entered an element deflectiondevice 155 via the diffusion optical system 120, the scanner 130 and thelight condensing optical system 140, a traveling direction of the lightis bent by the element deflection device 155, and the light travels to apredetermined element illumination area Zp. Particularly in the secondembodiment, light is diffused by the diffusion optical system 120, thena light path of the light is adjusted by the scanner 130, and the lightfurther is condensed by the light condensing optical system 140 so as toenter the element deflection device 155. Namely, as shown in FIG. 9,light incident on an element deflection device 155 at a certain instancehas an incident direction distribution corresponding to the dispersionangle θ_(x) of the optical axes d_(lf14) of the convergent light fluxeslf14. Thus, light emergent from the element deflection device 155 at acertain instance also has an angular distribution corresponding to apredetermined dispersion angle θ_(y). In addition, as shown in FIG. 9,light incident on the element deflection device 155 at a certaininstance enters the whole area of the spot area S having an arealbroadness to a certain degree. Thus, the light incident on the elementdeflection device 155 is diffused by the element deflection device 155,and can illuminate the whole area of a predetermined elementillumination area Zp.

An element illumination area Zp forms a part of the illumination area Z.An element illumination area Zp corresponding to one element deflectiondevice 155 is not at least partially overlapped with an elementillumination area Zp corresponding to another element deflection device155. Namely, an aggregation of the element illumination areas Zpcorresponding to a plurality of element deflection devices 155 providesthe illumination area Z that can be illuminated by the illuminationdevice 110.

FIG. 11 is a plan view showing the element deflection devices 155,together with the element illumination areas Zp to which light isdirected by the element deflection devices 155. In the example shown inFIG. 11, nine element deflection devices 155 are aligned along thelongitudinal directions of the respective light deflection devices 150a, 150 b and 150 c. The illumination area Z is planarly divided like agrid into nine element illumination areas Zp. That is to say, in theillustrated example, one element illumination area Zp is not overlappedwith another element illumination area Zp. First element deflectiondevices 155 a of the respective light deflection devices 150 a, 150 band 150 c illuminate a first element illumination area Zp1. Similarly,second to ninth element deflection devices 155 b to 155 i of therespective light deflection devices 150 a, 150 b and 150 c illuminatesecond to ninth element illumination areas Zp2 to Zp9.

Since a traveling direction of a laser light is changed by the scanner130 over time, as shown in FIG. 10, the laser lights (laser beams) scanthe light deflection devices 150 a, 150 b and 150 c along thelongitudinal directions of the light deflection devices 150 a, 150 b and150 c. As shown in FIG. 10, an area on the light deflection device 150irradiated with the laser light at a certain instance, i.e., a spot areaS has a planar dimension smaller than the element deflection device 155.The spot area S scans the first to ninth element deflection devices 155a to 155 i sequentially.

The light deflection device 150 is formed with the use of a diffractiongrating array 152, for example. In the example shown in FIGS. 7, 10 and11, three diffraction grating arrays 152 a, 152 b and 152 c are disposedcorrespondingly to the respective light deflection devices 150 a, 150 band 150 c. The respective diffraction grading arrays 152 a, 152 b and152 c are provided correspondingly to laser lights of differentwavelength ranges. By using laser lights of wavelength ranges which haveentered the whole area of the respective diffraction grating arrays 152a, 152 b and 152 c so as to be deflected, the whole area of the thecommon illumination area Z can be illuminated.

Each of the diffraction grating arrays 152 a, 152 b and 152 c issegmented into a plurality of the element deflection devices 155. Therespective element deflection devices 155 are formed of diffractiongratings 157 storing interference fringe patters different from oneanother. A laser light incident on each diffraction grating 157 isdiffracted by an interference fringe pattern and illuminates acorresponding element illumination area Zp in the illumination area Z.By variously adjusting the interference fringe patterns, a travelingdirection of a laser light that is diffracted by each diffractiongrating 157, in other words, a traveling direction of a laser light thatis deflected by each diffraction grating 157 can be controlled.

The diffraction grating 157 can be manufactured as a volume typehologram, for example. To be more specific, when a hologramphotosensitive material that is a matrix of the diffraction grating 157is irradiated with reference light and object light of coherent lightinterfering with each other, interference fringes by the lightinterference are formed on the hologram photosensitive material so thatthe diffraction grating 157 is manufactured.

By emitting laser light toward the element deflection device 155 suchthat the laser light travels reversely to the light path of thereference light that was used when the diffraction grating 157 wasmanufactured, diffraction light goes out from the diffraction grating157 reversely along the light path of the object light that was usedwhen the diffraction grating 157 was manufactured.

Instead of being formed by using real object light and reference light,a complicated interference fringe pattern formed on each diffractiongrating 157 can be designed by using a computer based on a wavelengthand an incident direction of expected illumination light to bereconstructed as well as a shape and a position of an image to bereconstructed. A diffraction grating 157 thus obtained is also referredto as computer generated hologram (CGH). In addition, a Fourierconversion hologram in which respective points on each diffractiongrating 157 have the same diffusion angle properties may be generated bya computer. Further, a size and a position of an actual illuminationrange may be set by disposing an optical member such as a lens behind anoptical axis of an element illumination area Zp.

One of the advantages of providing the diffraction grating 157 as theelement deflection device 155 is that a light energy density of laserlight can be decreased by diffusion. Another advantage is that thediffraction grating 157 can be used as a directional surface lightsource. In this case, as compared with a conventional lamp light source(point light source), a luminance on a light source surface forachieving the same illumination distribution can be decreased. Thus,safety of laser light can be improved. Namely, even when a person looksa laser light having passed through the element illumination area Zpwith his/her eyes, the eyes are less affected as compared with a case inwhich a person looks a single point light source with his/her eyes.

Next, an operation of the illumination device 110 as structured above isdescribed.

As shown in FIG. 7, based on a control signal from the emission controlunit 112, the respective light source units 117 a, 117 b and 117 coscillate laser lights (laser beams) of respective wavelength ranges.Laser lights going out from the laser light source 115 firstly traveltoward the diffusion optical system 120. In the example shown in FIG. 8,the laser lights of the respective wavelength ranges are shaped intoparallel light fluxes lf11 by the beam expander 121 and the collimationlens 122 of the diffusion optical system 120. Thereafter, each of theparallel light fluxes lf11 of the respective wavelength ranges isdivided into convergent light fluxes lf12 by the element lens 124 of thelens array 123. As to the laser lights of the respective wavelengthranges, the convergent light fluxes lf12 are similarly shaped, andoptical axes of d_(lf12) of the convergent light fluxes lf12 areparallel to one another.

The laser lights having been shaped by the diffusion optical system 120,i.e., the convergent light fluxes lf12 travel toward the polygonalmirror 131 forming the scanner 130. The polygonal mirror 131 isconsecutively rotated about the rotational axis line ra. Thus, aninclination angle of the reflection surface of the polygonal mirror 131is cyclically changed within a predetermined angular area. As a result,a direction of a laser light reflected by the polygonal mirror 131cyclically changes.

As shown in FIG. 8, the polygonal mirror 131 reflects the convergentlight fluxes lf12 on a position where the convergent light fluxes lf12converge, or on a position close thereto. Thus, since the convergentlight fluxes lf12 are reflected by the polygonal mirror 131, theconvergent light fluxes lf12 are converted into divergent light fluxeslf13 whose divergent points are located on the reflection position ofthe polygonal mirror 131, or on a position close thereto. Each of thesix reflection surfaces of the polygonal mirror 131 is large enough toreflect all the convergent light fluxes lf12 having been shaped by thediffusion optical system 120. Thus, as shown in FIG. 9, optical axesd_(lf13) of the divergent light fluxes lf13 that are the laser lightsreflected by the polygonal mirror 131 remain parallel. Since thepolygonal mirror 131 reflects the light fluxes lf13 that are in theconvergent state, enlargement of the polygonal mirror 131 can beeffectively avoided.

In addition, the polygonal mirror 131 includes the first reflection unit131 a, the second reflection unit 131 b and the third reflection unit131 c, along this rotational axis line ra. Since these reflection units131 a, 131 b and 131 c are synchronically operated, the laser light fromthe first light source unit 117 a, the laser light from the second lightsource unit 117 b and the laser light from the third light source unit117 c synchronically change their traveling directions.

As shown in FIG. 9, the divergent light fluxes lf13 with their lightpaths having been adjusted by the scanner 130 enter the light condensingoptical system 140. The optical axes d_(lf13) of the divergent lightfluxes lf13 remain parallel to one another. In addition, the lightdeflection device 150 is located on the focus Pf of the light condensinglens 141 forming the light condensing optical system 140. Thus, lightfluxes lf14 with their light paths having been adjusted by the lightcondensing lens 141 are condensed by the light condensing lens 141, andtheir optical axes d_(lf14) intersect on the light deflection device150. In particular, in the illustrated example, the reflection positionof the polygonal mirror 131 is located on a focus position behind thelight condensing lens 141, or on a position close thereto. Thus, thelight fluxes lf13 traveling from the polygonal mirror 131 toward thelight condensing lens 141 are converted to parallel light fluxes lf14 bythe lens effect of the light condensing lens 141. The parallel lightfluxes lf14 are overlapped with one another on the light deflectiondevice 150.

An area on which the parallel light fluxes lf14 are overlapped with oneanother on the light deflection device 150, i.e., a spot area S scansthe light deflection device 150 along the longitudinal direction of theelongate light deflection device 150, in conjunction with the operationof the scanner 130. As a result, as shown in FIG. 10, the laser lightssequentially irradiate the element deflection devices 155. The laserlight incident on each element deflection device 155 is deflected by theelement deflection device 155 so as to illuminate the whole area of anelement illumination area Zp corresponding to the element deflectiondevice 155.

The emission control unit 112 controls emission of laser lights from thelight source unit 117, depending on irradiation positions of laserlights on the light deflection device 150. Thus, only a desired elementillumination area Zp in the illumination area Z can be selected andilluminated. In addition, the emission control unit 112 can controlemission of light from the light source units 117 a, 117 b and 117 cindependently. Thus, it is also possible to illuminate a predeterminedelement illumination area Zp with light emitted from one(s) selectedfrom the first light source unit 117 a, the second light source unit 117b and the third light source unit 117 c. That is to say, each of thefirst to ninth element illumination areas Zp1 to Zp9 included in theillumination area Z can be adjusted independently from the other elementillumination areas, as to whether illuminated or not, the degree ofbrightness and the color of illumination light.

In order to simplify control of the scanner 130, the scanner 130 ispreferably operated such that a laser light can cyclically scan thewhole area of the light deflection device 150. In the example shown inFIG. 10, the scanner 130 is preferably operated such that a laser lightscans over the whole lengths of the light deflection devices 150 a, 150b and 150 c along the longitudinal directions of the light deflectiondevices 150 a, 150 b and 150 c. When only a predetermined elementillumination area Zp is desired to be illuminated, the emission controlunit 112 controls emission and stop of laser light of the laser lightsource 115, depending on the operation of the scanner 130, in otherwords, depending on a position on the light deflection device 150 to beirradiated with a laser light.

On the other hand, light emitted from a light source such as a laserlight source generally involves illuminance non-uniformity in a spotarea. Generally, as shown in FIG. 13, the center of the spot area Sp isbrightest, and it gradually darkens toward a periphery of the spot areaSp. Typically, an illuminance distribution is the Gaussian distributionfrom the center of the spot area Sp toward the periphery thereof.Namely, the spot area Sp has a large rim part of a low illuminance.Thus, as shown in FIG. 13, an effective scanning section scp1, in whichthe whole spot area Sp is located inside one element deflection device155 corresponding to a predetermined element illumination area Zp, isrelatively short. On the other hand, as shown in FIG. 13, an ineffectivescanning section scp2, in which only a part of the spot area Sp islocated within the one element deflection device 155, i.e., in theexample shown in FIG. 13, the ineffective scanning section scp2, inwhich the spot area Sp is located over two element deflection devices155 that are adjacent in a scanning direction sd, is relatively long. Inthe example shown in FIG. 13, the effective scanning section scp1 issignificantly shorter than the ineffective scanning section scp2.

In the example shown in FIG. 13, when only a predetermined elementillumination area Zp is illuminated, the emission control unit 112 emitsa laser light in such a manner that the center of the spot area Sp islocated within the effective scanning section scp1, while stops emissionof laser light in such a manner that the center of the spot area Sp islocated within the ineffective scanning section scp2. Thus, when thescanner 130 is operated at a constant speed, in the example shown inFIG. 13, a time period in which the emission of laser light is stoppedis significantly long. Namely, the laser light source 115 is notefficiently used. Further, in order to illuminate an elementillumination area Zp sufficiently brightly by emitting light in a shortperiod of time, it is necessary to prepare a high output laser lightsource.

In order to deal with this problem, the illumination device 110 in thesecond embodiment is equipped with the diffusion optical system 120 andthe scanner 130. The diffusion optical system 120 shapes light-sourcelight emitted from the laser light source 115. The light condensingoptical system 140 is located on a light path of light from thediffusion optical system 120 up to the light deflection device 150, andcondenses light-source light such that the spot area S on the lightdeflection device 150 is smaller than the element deflection device 155.Due to the diffusion optical system 120 and the scanner 130, it ispossible not only to regulate the shape and the size of the spot area Son the light deflection device 150, but also to make uniform anilluminance distribution of the spot area S.

Thus, as shown in FIG. 12, the effective scanning section sc1, in whichthe whole spot area S is located only within one element deflectiondevice 155 corresponding to a predetermined element illumination areaZp, can be made relatively long. On the other hand, as shown in FIG. 12,the ineffective scanning section scp2, in which only a part of the spotarea Sp is located within the one element deflection device 155, i.e.,in the illustrated example, the ineffective scanning section scp2, inwhich the spot area Sp is located over two element deflection devices155 that are adjacent in the scanning direction sd, can be maderelatively short. In the example shown in FIG. 12, the effectivescanning section sc1 is significantly longer than the ineffectivescanning section sc2. Thus, even when only a predetermined elementillumination area Zp is illuminated, a period of time in which a laserlight is emitted can be increased. Thus, it is possible to illuminatethe element defection device 155 sufficiently brightly by means of theefficient use of the laser light source 115, instead of using a highoutput laser light source 115. Thus, the performance of the laser lightsource 115 is sufficiently utilized so as to illuminate the illuminationarea Z in a desired light distribution pattern with a sufficientlybright quantity of light.

Particularly in the example shown in FIGS. 10 and 12, a size wsx of thespot area S along a direction parallel to the scanning direction sd ofthe spot area S is significantly smaller than a size wsy of the spotarea S along a direction orthogonal to the scanning direction sd of thespot area S, in particular, smaller than a half of the size wsy. In thedirection parallel to the scanning direction sd of the spot area S, thesize wsx of the spot area S is significantly smaller than a size wpx ofthe element deflection device 155, in particular, smaller than a half ofthe size wpx. Thus, the ineffective scanning section sc2, in which onlya part of the spot area S is located within the one element deflectiondevice 155, can be made very short. Therefore, according to the exampleshown in FIGS. 10 and 12, a period of time in which the laser lightsource 115 stops emission of laser light can be significantly madeshort. That is to say, the laser light source 115 can be moreefficiently utilized.

In addition, as shown in FIG. 12, in the direction orthogonal to thescanning direction sd of the spot area S, the size wsy of the spot areaS is substantially the same as or slightly smaller than the size wpy ofthe element deflection device 155. Thus, most of the light deflectiondevice 150 can be irradiated with light-source light, in conjunctionwith the operation of the scanner 130. Namely the whole surface of thelight deflection device 150 can be efficiently utilized, so as to avoidenlargement of the illumination device 110.

As described above, in the second embodiment, the illumination device110 includes the diffusion optical system 120 that diffuses light-sourcelight emitted from the light source, and the light condensing opticalsystem 140 located on a light path of light-source light from thediffusion optical system 120 up to the light deflection device 150. Thelight condensing optical system 140 condenses light-source light suchthat the spot area S on the light deflection device 150 is smaller thanthe element deflection device 155. Each element deflection device 155adjusts a light path of light-source light incident thereon so as toilluminate an element illumination area Zp corresponding to the elementdeflection device 155. According to the second embodiment, the shape ofthe spot area S and the illuminance distribution of the spot area S canbe adjusted by the diffusion optical system 120 and the light condensingoptical system 140. As a result, the performance of the laser lightsource 115 is sufficiently utilized so as to illuminate the illuminationarea Z in a desired light distribution pattern with a sufficientlybright quantity of light.

In addition, in the second embodiment, the diffusion optical system 120divides light-source light emitted from the light source 115 into lightfluxes lf12. The light condensing optical system 140 adjusts light pathsof light fluxes lf13 such that the light fluxes f113 are at leastpartially overlapped on the light deflection device 150. Thus, even whenan illuminance distribution of the light-source light upon emission fromthe light source 115 is non-uniform, since the illuminance distributionis divided and overlapped, the illuminance distribution can beeffectively made uniform. In particular, when the illuminancedistribution of the light-source light upon emission from the lightsource 115 is the typical Gaussian distribution, the illuminancedistribution is planarly divided and overlapped, so that the illuminancedistribution can be significantly effectively made uniform. Thus, theillumination area Z can be more brightly illuminated with a desiredlight distribution pattern.

Further, in the second embodiment, the light condensing optical system140 is the lens 141 having the focus position Pf on which the lightdeflection device 150 is located. According to such a light condensingoptical system 140, although it has a simple structure, light incidenton the light condensing optical system 140 at a given instance can becondensed highly efficiently on the spot area S on the light condensingoptical system 140, so that the illuminance distribution of the spotarea S can be effectively made uniform.

Further, in the second embodiment, the diffusion optical system 120includes the collimation lens 122, and the lens array 123 located on alight path from the collimation lens 122 up to the light condensingoptical system 140. According to such a diffusion optical system 120,the optical axes d_(lf13) of the light fluxes lf13 incident on the lightcondensing optical system 140 can be made parallel. In this case, bymeans of the light condensing optical system 140 using the lightcondensing lens 141, the optical axes d_(lf14) of the light fluxes,which have been shaped by the diffusion optical system 120, can beallowed to intersect on the light deflection device 150. Thus, theilluminance distribution of the spot area S can be more effectively madeuniform.

In addition, by adjusting the width w_(lf11) (see FIG. 8) of theparallel light flux lf11 by the beam expander 121 and the collimationlens 122, a dispersion angle θ (see FIG. 10) of the optical axesd_(lf14) of the convergent light fluxes lf14 incident on the lightcondensing lens 141 can be controlled. Thus, it is possible to shapeillumination light going out from the element deflection device 155 toadjust a dispersion angle θ_(y) of the illumination light. Further, itis possible to adjust the size of a spot area S to be illuminated by theillumination light, and a brightness distribution in the spot area S.

Further, in the second embodiment, the lens array 123 includes theelement lenses 124. The light fluxes lf12 emergent from the elementlenses 124 can be the same light distributions each other. In this case,by means of the light condensing optical system 140 using the lightcondensing lens 141, the light fluxes which have been shaped by thediffusion optical system 120 can be highly precisely overlapped with oneanother on the light deflection device 150. Thus, the shape of the spotarea S can be more precisely adjusted, and the illuminance distributionof the spot area S can be more effectively made uniform.

In addition, by suitably positioning the light condensing optical system140 and the scanner 130 and by suitably designing the element lens 124so as to adjust the convergent angle θ_(lf12) of the convergent lightflux lf12 having been shaped by the element lens 124, the width wsx (seeFIG. 10) of the spot area S can be controlled. In particular, byadjusting the convergent angle θ_(lf12) of the convergent light fluxlf12 having been shaped by the element lens 124, the width wsx of thespot area S can be adjusted while effectively avoiding enlargement ofthe illumination device 110. Thus, it is possible to shape illuminationlight going out from the element deflection device 155. Further, it ispossible to adjust the size of a spot area S to be illuminated by theillumination light, and a brightness distribution in the spot area S.

The aforementioned second embodiment can be variously modified.Modification examples are described herebelow. In the drawings used inthe below description, a component that can be similarly structured asthat of the above embodiment has the same reference number as the numberused for the corresponding component of the above embodiment, andredundant description is omitted.

In the aforementioned second embodiment, there is shown the example inwhich the diffusion optical system 120 includes the beam expander 121,the collimation lens 122 and the lens array 123. However, the presentinvention is not limited to this example. The diffusion optical system120 may be made of a beam homogenizer 125 that forms a uniform intensitydistribution. As the beam homogenizer 125, a member using diffractiveoptical elements (DOE) or a member using an aspherical lens or afree-form surface lens can be employed.

In addition, in the aforementioned second embodiment, there is shown theexample in which the light deflection device 150 is made of thediffraction grating array 152. However, the present invention is notlimited to this example. For example, the light deflection device 150may be made by using a prism array in which the respective elementdeflection devices 155 constitute one prism. In this case, a prism isprovided for each element deflection device 155, and the shape of eachprism is designed such that each prism illuminates an elementillumination area Zp in the illumination area Z. Positions of therespective element illumination areas Zp are at least partiallydifferent.

Further, in the aforementioned second embodiment, there is shown theexample in which the element deflection device 155 has a light pathadjustment function for directing a traveling direction of light, whichhas been incident thereon from a certain direction, toward apredetermined direction. However, not limited thereto, the elementdeflection device 155 may have a diffusion property. For example, theelement deflection device 155 may direct a traveling direction of light,which has been incident thereon from a certain direction, toward a rangehaving an angular distribution about a predetermined direction. In thisexample, light emergent from the element deflection device 155 may havea maximum luminance in a predetermined direction, and a luminance oflight emergent in a direction inclined to the predetermined directionmay decrease as an inclination angle with respect to the predetermineddirection increases.

Further, in the aforementioned second embodiment, there is shown theexample in which the polygonal mirror 131 reflects a laser light on aposition apart from the element lens 124 by the focus distance of theelement lens 124 along the optical axis d₁₂₄ of the element lens 124.However, the present invention is not limited to this example. Inaddition, in the aforementioned first embodiment, there is shown theexample in which the polygonal mirror 131 reflects a laser light at aposition apart from the light condensing lens 141 by the focus distanceof the light condensing lens 141 along the optical axes d₁₄₀ of thelight condensing lens 141. However, the present invention is not limitedto this example. For example, the light condensing lens 141 may belocated on a light path from the element lens 124 toward the scanner130. In addition, the lens array 123 including the element lenses 124may be located on a light path from the scanner 130 toward the lightcondensing optical system 140.

Further, in the aforementioned second embodiment, there is shown theexample in which the light condensing optical system 140 is formed of aconvex lens. However, the present invention is not limited thereto. Forexample, the light condensing optical system 140 may be formed of aconcave mirror.

Further, in the aforementioned second embodiment, there is shown theexample in which the laser light source 115 as a light source emitslaser light (laser beams) of a plurality of wavelength ranges. However,the present invention is not limited thereto. The light source may be alight source that emits light of the same wavelength range.

Further, the above-described illumination device 110 may be mounted on aconveyance, or installed at a predetermined location. When it is mountedon a conveyance, the conveyance may be various moving bodies such as avehicle like an automobile, a flying body like an aircraft, a train, aship, a diving body and so on.

Although some modification examples of the second embodiment have beendescribed above, the modification examples can be naturally combined andused.

1. An illumination device comprising: a light diffusion device includingelement diffusion devices that diffuse incident light; a coherent lightsource that emits coherent light; a shaping optical system that shapesthe coherent light; a scanner that adjusts a traveling direction of thecoherent light so as to allow the coherent light to scan the lightdiffusion device; and a light condensing optical system located on alight path of the coherent light from the shaping optical system up tothe light diffusion device; wherein: the light condensing optical systemcondenses the coherent light such that a spot area on the lightdiffusion device is smaller than the element diffusion device; and eachelement diffusion device diffuses the coherent light incident thereon soas to illuminate an element illumination area corresponding to theelement diffusion device.
 2. The illumination device according to claim1, wherein: the shaping optical system divides the coherent lightemitted from the coherent light source into light fluxes; and the lightcondensing optical system adjusts light paths of the light fluxes suchthat the light fluxes are overlapped at least partially on the lightdiffusion device.
 3. The illumination device according to claim 1,wherein the light condensing optical system includes a lens, and thelight diffusion device is located on a focus position of the lens. 4.The illumination device according to claim 1, wherein the shapingoptical system includes a collimation lens, and a lens array located ona light path from the collimation lens up to the light condensingoptical system.
 5. The illumination device according to claim 4,wherein: the lens array includes element lenses; and light fluxesemergent from the element lenses have the same light distributions. 6.The illumination device according to claim 1, wherein the shapingoptical system has a beam homogenizer.
 7. The illumination deviceaccording to claim 1, further comprising an emission control unit thatcontrols emission of the coherent light from the coherent light source.8. The illumination device according to claim 7, wherein the emissioncontrol unit controls emission of the coherent light of the coherentlight source, depending on an irradiation position of the coherent lighton the light diffusion device.
 9. The illumination device according toclaim 1, wherein: the light diffusion device has a hologram storagemedium; and the element diffusion devices are element holograms havinginterference fringe patterns different from one another.
 10. Theillumination device according to claim 1, wherein: the light diffusiondevice has a lens array group including a plurality of lens arrays; andthe element diffusion devices have the lens arrays.
 11. An illuminationdevice comprising: a light deflection device including elementdeflection devices that adjust a traveling direction of incident light;a light source; a diffusion optical system that diffuses light-sourcelight emitted by the light source; a scanner that adjusts a travelingdirection of the light-source light so as to so as to allow thelight-source light to scan the light deflection device; and a lightcondensing optical system located on a light path of the light-sourcelight from the diffusion optical system up to the light deflectiondevice; wherein: the light condensing optical system condenses thelight-source light such that a spot area on the light deflection deviceis smaller than the element deflection device; and each elementdeflection device adjusts a traveling direction of the light-sourcelight incident thereon so as to illuminate an element illumination areacorresponding to the element deflection device.
 12. The illuminationdevice according to claim 11, wherein: the diffusion optical systemdivides the light-source light into light fluxes; and the lightcondensing optical system adjusts light paths of the light fluxes suchthat the light fluxes are overlapped at least partially on the lightdeflection device.
 13. The illumination device according to claim 11,wherein the light condensing optical system includes a lens, and thelight deflection device is located on a focus position of the lens. 14.The illumination device according to claim 11, wherein the diffusionoptical system includes a collimation lens, and a lens array located ona light path from the collimation lens up to the light condensingoptical system.
 15. The illumination device according to claim 14,wherein: the lens array includes element lenses; and light fluxesemergent from the element lenses have the same light distributions. 16.The illumination device according to claim 11, wherein the diffusionoptical system has a beam homogenizer.
 17. The illumination deviceaccording to claim 11, further comprising an emission control unit thatcontrols emission of light from the light source.
 18. The illuminationdevice according to claim 17, wherein the emission control unit controlsemission of light from the light source, depending on an irradiationposition of the light-source light on the light deflection device. 19.The illumination device according to claim 11, wherein: the lightdeflection device has a diffraction grating array; and each elementdeflection device is a diffraction grating.
 20. The illumination deviceaccording to claim 11, wherein: the light deflection device has a prismarray; and each element deflection device is a prism.